def _lfunction(self, W, prec=53, threshold=1e-10):
from sage.lfunctions.all import Dokchitser
G = self.domain()
LG = G.splitting_field()
deg = self.degree()
#Determine the Gamma factors
if LG.is_totally_real():
gammaV = [0] * deg
else:
H = G.subgroup([G.complex_conjugation(LG.places()[0])])
deg_plus = ZZ(self.restrict(H).scalar_product(H.trivial_character()))
gammaV = [0] * deg_plus + [1] * (deg - deg_plus)
if self.scalar_product(G.trivial_character()) > 0:
raise NotImplementedError
L = Dokchitser(conductor=self.conductor(), gammaV=gammaV, weight=1, eps=W, prec=prec)
coeffs = 'coeff = %s'%(self.dirichlet_coefficients(L.num_coeffs(1.2)))
L.init_coeffs('coeff[k]', pari_precode=coeffs)
if L.check_functional_equation().abs() > threshold:
return None
self._root_number = W
return True
#self._lfunction = L
pass
def eisenstein_series_lseries(weight, prec=53,
max_imaginary_part=0,
max_asymp_coeffs=40):
r"""
Return the L-series of the weight `2k` Eisenstein series
on `\mathrm{SL}_2(\ZZ)`.
This actually returns an interface to Tim Dokchitser's program
for computing with the L-series of the Eisenstein series
INPUT:
- ``weight`` - even integer
- ``prec`` - integer (bits precision)
- ``max_imaginary_part`` - real number
- ``max_asymp_coeffs`` - integer
OUTPUT:
The L-series of the Eisenstein series.
EXAMPLES:
We compute with the L-series of `E_{16}` and then `E_{20}`::
sage: L = eisenstein_series_lseries(16)
sage: L(1)
-0.291657724743874
sage: L = eisenstein_series_lseries(20)
sage: L(2)
-5.02355351645998
Now with higher precision::
sage: L = eisenstein_series_lseries(20, prec=200)
sage: L(2)
-5.0235535164599797471968418348135050804419155747868718371029
"""
f = eisenstein_series_qexp(weight,prec)
from sage.lfunctions.all import Dokchitser
from sage.symbolic.constants import pi
key = (prec, max_imaginary_part, max_asymp_coeffs)
j = weight
L = Dokchitser(conductor = 1,
gammaV = [0,1],
weight = j,
eps = (-1)**Integer(j/2),
poles = [j],
# Using a string for residues is a hack but it works well
# since this will make PARI/GP compute sqrt(pi) with the
# right precision.
residues = '[sqrt(Pi)*(%s)]'%((-1)**Integer(j/2)*bernoulli(j)/j),
prec = prec)
s = 'coeff = %s;'%f.list()
L.init_coeffs('coeff[k+1]',pari_precode = s,
max_imaginary_part=max_imaginary_part,
max_asymp_coeffs=max_asymp_coeffs)
L.check_functional_equation()
L.rename('L-series associated to the weight %s Eisenstein series %s on SL_2(Z)'%(j,f))
return L
def eisenstein_series_lseries(weight, prec=53,
max_imaginary_part=0,
max_asymp_coeffs=40):
r"""
Return the L-series of the weight `2k` Eisenstein series
on `\mathrm{SL}_2(\ZZ)`.
This actually returns an interface to Tim Dokchitser's program
for computing with the L-series of the Eisenstein series
INPUT:
- ``weight`` - even integer
- ``prec`` - integer (bits precision)
- ``max_imaginary_part`` - real number
- ``max_asymp_coeffs`` - integer
OUTPUT:
The L-series of the Eisenstein series.
EXAMPLES:
We compute with the L-series of `E_{16}` and then `E_{20}`::
sage: L = eisenstein_series_lseries(16)
sage: L(1)
-0.291657724743874
sage: L = eisenstein_series_lseries(20)
sage: L(2)
-5.02355351645998
Now with higher precision::
sage: L = eisenstein_series_lseries(20, prec=200)
sage: L(2)
-5.0235535164599797471968418348135050804419155747868718371029
"""
f = eisenstein_series_qexp(weight,prec)
from sage.lfunctions.all import Dokchitser
from sage.symbolic.constants import pi
key = (prec, max_imaginary_part, max_asymp_coeffs)
j = weight
L = Dokchitser(conductor = 1,
gammaV = [0,1],
weight = j,
eps = (-1)**Integer(j/2),
poles = [j],
# Using a string for residues is a hack but it works well
# since this will make PARI/GP compute sqrt(pi) with the
# right precision.
residues = '[sqrt(Pi)*(%s)]'%((-1)**Integer(j/2)*bernoulli(j)/j),
prec = prec)
s = 'coeff = %s;'%f.list()
L.init_coeffs('coeff[k+1]',pari_precode = s,
max_imaginary_part=max_imaginary_part,
max_asymp_coeffs=max_asymp_coeffs)
L.check_functional_equation()
L.rename('L-series associated to the weight %s Eisenstein series %s on SL_2(Z)'%(j,f))
return L
def dokchitser(self,
prec=53,
max_imaginary_part=0,
max_asymp_coeffs=40,
algorithm='gp'):
r"""
Return interface to Tim Dokchitser's program for computing
with the `L`-series of this elliptic curve; this provides a way
to compute Taylor expansions and higher derivatives of
`L`-series.
INPUT:
- ``prec`` -- integer (bits precision)
- ``max_imaginary_part`` -- real number
- ``max_asymp_coeffs`` -- integer
- ``algorithm`` -- string: 'gp' or 'magma'
.. note::
If algorithm='magma', then the precision is in digits rather
than bits and the object returned is a Magma L-series, which has
different functionality from the Sage L-series.
EXAMPLES::
sage: E = EllipticCurve('37a')
sage: L = E.lseries().dokchitser()
sage: L(2)
0.381575408260711
sage: L = E.lseries().dokchitser(algorithm='magma') # optional - magma
sage: L.Evaluate(2) # optional - magma
0.38157540826071121129371040958008663667709753398892116
If the curve has too large a conductor, it isn't possible to
compute with the `L`-series using this command. Instead a
``RuntimeError`` is raised::
sage: e = EllipticCurve([1,1,0,-63900,-1964465932632])
sage: L = e.lseries().dokchitser(15)
Traceback (most recent call last):
...
RuntimeError: Unable to create L-series, due to precision or other limits in PARI.
"""
if algorithm == 'magma':
from sage.interfaces.all import magma
return magma(self.__E).LSeries(Precision=prec)
from sage.lfunctions.all import Dokchitser
key = (prec, max_imaginary_part, max_asymp_coeffs)
try:
return self.__dokchitser[key]
except KeyError:
pass
except AttributeError:
self.__dokchitser = {}
L = Dokchitser(conductor=self.__E.conductor(),
gammaV=[0, 1],
weight=2,
eps=self.__E.root_number(),
poles=[],
prec=prec)
gp = L.gp()
s = 'e = ellinit(%s);' % list(self.__E.minimal_model().a_invariants())
s += 'a(k) = ellak(e, k);'
L.init_coeffs('a(k)',
1,
pari_precode=s,
max_imaginary_part=max_imaginary_part,
max_asymp_coeffs=max_asymp_coeffs)
L.rename('Dokchitser L-function associated to %s' % self.__E)
self.__dokchitser[key] = L
return L
def dokchitser(self, prec=53,
max_imaginary_part=0,
max_asymp_coeffs=40,
algorithm='gp'):
r"""
Return interface to Tim Dokchitser's program for computing
with the L-series of this elliptic curve; this provides a way
to compute Taylor expansions and higher derivatives of
$L$-series.
INPUT:
prec -- integer (bits precision)
max_imaginary_part -- real number
max_asymp_coeffs -- integer
algorithm -- string: 'gp' or 'magma'
\note{If algorithm='magma', then the precision is in digits rather
than bits and the object returned is a Magma L-series, which has
different functionality from the Sage L-series.}
EXAMPLES::
sage: E = EllipticCurve('37a')
sage: L = E.lseries().dokchitser()
sage: L(2)
0.381575408260711
sage: L = E.lseries().dokchitser(algorithm='magma') # optional - magma
sage: L.Evaluate(2) # optional - magma
0.38157540826071121129371040958008663667709753398892116
If the curve has too large a conductor, it isn't possible to
compute with the L-series using this command. Instead a
RuntimeError is raised::
sage: e = EllipticCurve([1,1,0,-63900,-1964465932632])
sage: L = e.lseries().dokchitser(15)
Traceback (most recent call last):
...
RuntimeError: Unable to create L-series, due to precision or other limits in PARI.
"""
if algorithm == 'magma':
from sage.interfaces.all import magma
return magma(self.__E).LSeries(Precision = prec)
from sage.lfunctions.all import Dokchitser
key = (prec, max_imaginary_part, max_asymp_coeffs)
try:
return self.__dokchitser[key]
except KeyError:
pass
except AttributeError:
self.__dokchitser = {}
L = Dokchitser(conductor = self.__E.conductor(),
gammaV = [0,1],
weight = 2,
eps = self.__E.root_number(),
poles = [],
prec = prec)
gp = L.gp()
s = 'e = ellinit(%s);'%list(self.__E.minimal_model().a_invariants())
s += 'a(k) = ellak(e, k);'
L.init_coeffs('a(k)', 1, pari_precode = s,
max_imaginary_part=max_imaginary_part,
max_asymp_coeffs=max_asymp_coeffs)
L.rename('Dokchitser L-function associated to %s'%self.__E)
self.__dokchitser[key] = L
return L
def zeta_function(self,
prec=53,
max_imaginary_part=0,
max_asymp_coeffs=40,
algorithm='pari'):
r"""
Return the Dedekind zeta function of this number field.
Actually, this returns an interface for computing with the
Dedekind zeta function `\zeta_F(s)` of the number field `F`.
INPUT:
- ``prec`` -- optional integer (default 53) bits precision
- ``max_imaginary_part`` -- optional real number (default 0)
- ``max_asymp_coeffs`` -- optional integer (default 40)
- ``algorithm`` -- optional (default "pari") either "gp" or "pari"
OUTPUT: The zeta function of this number field.
If algorithm is "gp", this returns an interface to Tim
Dokchitser's gp script for computing with L-functions.
If algorithm is "pari", this returns instead an interface to Pari's
own general implementation of L-functions.
EXAMPLES::
sage: K.<a> = NumberField(ZZ['x'].0^2+ZZ['x'].0-1)
sage: Z = K.zeta_function(); Z
PARI zeta function associated to Number Field in a with defining polynomial x^2 + x - 1
sage: Z(-1)
0.0333333333333333
sage: L.<a, b, c> = NumberField([x^2 - 5, x^2 + 3, x^2 + 1])
sage: Z = L.zeta_function()
sage: Z(5)
1.00199015670185
Using the algorithm "pari"::
sage: K.<a> = NumberField(ZZ['x'].0^2+ZZ['x'].0-1)
sage: Z = K.zeta_function(algorithm="pari")
sage: Z(-1)
0.0333333333333333
sage: L.<a, b, c> = NumberField([x^2 - 5, x^2 + 3, x^2 + 1])
sage: Z = L.zeta_function(algorithm="pari")
sage: Z(5)
1.00199015670185
TESTS::
sage: QQ.zeta_function()
PARI zeta function associated to Rational Field
"""
if algorithm == 'gp':
from sage.lfunctions.all import Dokchitser
r1, r2 = self.signature()
zero = [0]
one = [1]
Z = Dokchitser(conductor=abs(self.absolute_discriminant()),
gammaV=(r1 + r2) * zero + r2 * one,
weight=1,
eps=1,
poles=[1],
prec=prec)
s = 'nf = nfinit(%s);' % self.absolute_polynomial()
s += 'dzk = dirzetak(nf,cflength());'
Z.init_coeffs('dzk[k]',
pari_precode=s,
max_imaginary_part=max_imaginary_part,
max_asymp_coeffs=max_asymp_coeffs)
Z.check_functional_equation()
Z.rename('Dokchitser Zeta function associated to %s' % self)
return Z
if algorithm == 'pari':
from sage.lfunctions.pari import lfun_number_field, LFunction
Z = LFunction(lfun_number_field(self), prec=prec)
Z.rename('PARI zeta function associated to %s' % self)
return Z
raise ValueError('algorithm must be "gp" or "pari"')